Mechanical characteristic of conventional and geopolymer modified uhpc and design code assessment of axially loaded composite members with such concrete

The need for developing new structural members having high performance has gained significant attention in the construction industry all over the world. This thesis covers the material aspects of ultra-high performance conventional and geopolymer concrete (UHPC/UHPGC) and the structural aspects of the composite columns in the case of UHPC/UHPGC used as an infill. For this, the experimental and numerical works were carried out. The experimental work included two phases aim to investigate the possibility of producing and developing UHPC/UHPGC. In the first, a total of 11 conventional UHPC mixes were designed with different binder type and content at fixed micro steel fiber volume fraction. Whereas in the second, a total of 10 UHPGC mixtures were produced with the same parameters used in the first, but with a constant material/alkaline solution ratio. Three curing methods were adopted for the specimens and then they were tested for identifying the material characterization. On the other hand, the numerical work included the structural behavior of the steel tubular columns infilled with conventional and geopolymer modified UHPC. For the composite columns, circular cross-section with fixed slenderness ratio and wall thickness were taken account. However, the diameter to wall thickness ratio and yield strength of the steel tubes varied. Furthermore, a special theoretical procedure was adopted to take the benefit of compressive strength results on the axial behavior of CFST column. Three international design codes of ACI-318R, Eurocode 4 and Chinese code DL/T were used to evaluate and discuss the performance of the composite compression members.